TECHNET Archives

November 2012

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
"Stadem, Richard D." <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Stadem, Richard D.
Date:
Tue, 6 Nov 2012 18:51:09 +0000
Content-Type:
text/plain
Parts/Attachments:
text/plain (222 lines)
That is commonly known. The fix is to either use kapton tape or peelable maskant to cover the vent holes during assembly and rework. But yes, Bob's point is certainly well taken; one must know what one is working with before performing BGA assembly and rework.

Another little known fact: many BGAs have an electronic over-temperature switch built in to the chip. If the chip senses that the package is too hot or the temperature ramps up too quickly while powered up, it will shut down the BGA. 
On some of these, all it takes is touching the top of the package to cause that to happen, causing many test/troubleshooting techs to assume there is a cold or intermittent solder joint under the part.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bob Landman
Sent: Tuesday, November 06, 2012 11:43 AM
To: [log in to unmask]
Subject: Re: [TN] Limits on flux residue

Just remember some large metal lidded IC manufacturers proscribe no-clean to attach their parts as the lids are vented.  Read the fine print.  No warranty if you wash the parts.  

Wash water, even just DI water, that gets under the lids washes contamination into the parts and then dendritic growth can/does occur.

A company claims to have a patent pending process to allow these chips to be washed,  but no information is available on the process. Some suspect it is a one way vent valve.

The reason the lids are vented, as I recall (I have a paper on the subject) is that during reflow, the internal substrate (solder mask on the FR board as these complex ICs have decoupling caps and other discrete parts in addition to the silicon which is flip chip ball soldered to the board ) out gasses as its not fully cured and will blow the lid off the part.

Bob Landman
H&L Instruments,LLC
LDF Coatings, LLC

Sent from my iPhone

On Nov 6, 2012, at 11:31 AM, Brian Ellis <[log in to unmask]> wrote:

> On top of flux residue? NEVER, ever!!!!
> 
> On 06/11/2012 17:11, Joyce Koo wrote:
>> Conformal coat.
>> 
>> Joyce Koo
>> Materials Researcher - Materials Interconnect Lab Research In Motion 
>> Limited
>> Office: (519) 888-7465 79945
>> Mobile: (226) 220-4760
>> 
>> 
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, M. D. 
>> (M.)
>> Sent: Tuesday, November 06, 2012 10:07 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Limits on flux residue
>> 
>>> From my company's experience a humid condition and sulfur (H@S, 
>>> SO4-) in
>> the atmosphere can accelerate the process. Sulfurous gasses can be 
>> found in the far east (China, India, and others) from coal fired 
>> power generating plants, oil refineries, oil pumps stations and from 
>> vulcanization of rubber). We have found that in the far east the air 
>> conditioning of the building is turned off at nights and weekends.  
>> We have found evidence of condensation on vias from the humid 
>> atmosphere being taken in by the cooling fans while the metal is 
>> still cold enough to produce local saturation and condensation.  We 
>> are working with our customers to have the air conditioning on all 
>> the time, or at least dehumidify the incoming air to the point that 
>> water will not condense on the PWBs' vias at their "cool" temperature.
>> mark
>> 
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
>> Sent: Tuesday, November 06, 2012 7:56 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Limits on flux residue
>> 
>> Folks,
>> 
>>    A ticking time bomb for leakage and/or perhaps corrosion!   How can
>> you determine/predict when the two events will occur?   What the worst
>> case environment that will active either attribute?
>> 
>> Victor,
>> 
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
>> Sent: Tuesday, November 06, 2012 8:15 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Limits on flux residue
>> 
>> Dave, I could not agree with you more. Excellent posting, and 
>> excellent philosophy.
>> 
>> Too many times I hear someone say "who cares, its no-clean, perfectly 
>> safe" only to find the hard way that is not true.
>> Not only that, but most no-clean fluxes are very effective when 
>> applied as a very, very thin sheen or veneer (less than 1 mil thick) 
>> over the BGA pads. You DON'T need gobs, more flux does not mean better wetting.
>> Too much also means a better chance that not all of it will be 
>> heat-activated.
>> 
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
>> Sent: Tuesday, November 06, 2012 7:27 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Limits on flux residue
>> 
>> Hi Wayne - no, the JSTD-001 committee has not addressed that aspect 
>> of No Clean processing because there are a number of product use 
>> environment influences and process parameters that come into play on 
>> what is acceptable and unacceptable. Your description would lead me 
>> to believe that someone has taken extreme liberty in calling 
>> something a "no clean"
>> process. One of the things that we have found most interesting in the 
>> implementation of a no clean process for a couple of our products is 
>> that many folks believe "no clean" is a sloppy process and you can 
>> leave flux residue anywhere on the assembly in uncontrolled 
>> quantities. But the reality is that "no clean" solder processing 
>> requires very careful control of what/how much/where you allow flux 
>> residues to exist. In my view, a "no clean" process actually is a 
>> much tighter controlled process than a process that utilizes cleaning 
>> to insure that product functionality is not impacted.
>> 
>> Dave Hillman
>> Rockwell Collins
>> [log in to unmask]
>> 
>> 
>> 
>> From:   "Thayer, Wayne - IS" <[log in to unmask]>
>> To:     <[log in to unmask]>
>> Date:   11/05/2012 05:52 PM
>> Subject:        [TN] Limits on flux residue
>> Sent by:        TechNet <[log in to unmask]>
>> 
>> 
>> 
>> Is there a spec somewhere which limits the amount of residue allowed 
>> for no clean processing?  I just saw a board where a BGA was about 
>> 70% "underfilled" by flux residue.  No, this was not a flux/underfill 
>> product!
>>  A quick look at JSTD-001 Section 8 didn't seem to have specific 
>> guidance on this condition.
>> 
>> Wayne Thayer
>> 
>> ________________________________
>> 
>> Email addresses of ITT Exelis employees have changed from itt.com to 
>> exelisinc.com. Please update your favorites and contact information 
>> to reflect these changes.
>> 
>> This e-mail and any files transmitted with it may be proprietary and 
>> are intended solely for the use of the individual or entity to whom 
>> they are addressed. If you have received this e-mail in error please 
>> notify the sender. Please note that any views or opinions presented 
>> in this e-mail are solely those of the author and do not necessarily 
>> represent those of Exelis Inc. The recipient should check this e-mail 
>> and any attachments for the presence of viruses. Exelis Inc. accepts 
>> no liability for any damage caused by any virus transmitted by this e-mail.
>> 
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud 
>> service.
>> For more information please contact helpdesk at x2960 or 
>> [log in to unmask] 
>> _____________________________________________________________________
>> _
>> 
>> 
>> 
>> 
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud 
>> service.
>> For more information please contact helpdesk at x2960 or 
>> [log in to unmask] 
>> _____________________________________________________________________
>> _
>> 
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud 
>> service.
>> For more information please contact helpdesk at x2960 or 
>> [log in to unmask] 
>> _____________________________________________________________________
>> _
>> 
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud 
>> service.
>> For more information please contact helpdesk at x2960 or 
>> [log in to unmask] 
>> _____________________________________________________________________
>> _
>> 
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud 
>> service.
>> For more information please contact helpdesk at x2960 or 
>> [log in to unmask] 
>> _____________________________________________________________________
>> _
>> 
>> ---------------------------------------------------------------------
>> This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful.
>> 
>> _____________________________________________________________________
>> _ This email has been scanned by the Symantec Email Security.cloud 
>> service.
>> For more information please contact helpdesk at x2960 or 
>> [log in to unmask] 
>> _____________________________________________________________________
>> _
> 
> ______________________________________________________________________
> This email has been scanned by the Symantec Email Security.cloud service.
> For more information please contact helpdesk at x2960 or 
> [log in to unmask] 
> ______________________________________________________________________
> 

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

ATOM RSS1 RSS2